lighttpd not accessible from internet

[raas]

Hi,

i have 2 webservers running:
lighttpd on port 81
thttpd on port 8081

in my modem/firewall I created rules:
outside port 80 to inside port 8081
outside port 81 to inside port 81
(to the ip of the asus resp.)

now. port 80 is accessible from the internet.. it serves a page (thttpd)
port 81 is not accessible from the internet.. connection lost to the host.

from the internal network everything works fine. lighttpd serves a page.

I have lighttpd in a SSL/HTTPS setup, which requires a certificate. once accepted it will serve the page.. will do that from every pc in the internal network..
now the internet.... not.

I've search the config file if there was an option to exclude certain ip-ranges from the lighttpd server, but couldn't find anything..

anyone out there knows how to fix this problem?

the asus is set up as an accesspoint-only..
not using any firewall or anything..

Thanks in advance.